1. Field of the Invention
This invention generally relates to a polymeric composition comprising at least one phosphoryl choline moiety that is useful for coating an implantable device such as a drug eluting stent.
2. Description of the Background
Implanted stents have been used to carry medicinal agents, such as thrombolytic agents. U.S. Pat. No. 5,163,952 to Froix discloses a thermal-memoried expanding plastic stent device formulated to carry a medicinal agent in the material of the stent itself. Pinchuk, in U.S. Pat. No. 5,092,877, discloses a stent of a polymeric material which may have a coating associated with the delivery of drugs. Other patents which are directed to devices of the class utilizing bio-degradable or bio-absorbable polymers include Tang et al., U.S. Pat. No. 4,916,193, and MacGregor, U.S. Pat. No. 4,994,071.
Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels, such as by employing a stent. Stents are used not only for mechanical intervention but also as vehicles for providing biological therapy, e.g., a controlled delivery of agents. To effect a controlled delivery of an active agent in stent based therapy, the stent can be coated with a biocompatible polymeric coating. The biocompatible polymeric coating can function either as a permeable layer or a carrier to allow a controlled delivery of the agent. A continuing challenge in the art of implantable stents is to provide a coating that possesses good biobeneficial properties, which refer to good biocompatibilities in both the acute and chronic timeframes.
Generally, a polymer forming a coating composition for an implantable device has to be at least biologically benign. The polymer is preferably biocompatible. To provide for a coating that is biologically benign, various compositions have been used with limited success.
The polymer and methods of making the polymer disclosed herein address the above described problems.